This invention relates generally to communications between nodes in a network, and more specifically, to methods and apparatus for network joining using a multiple message per time division multiple access (TDMA) slot methodology.
Constructing a mobile ad hoc network (MANet) that includes multiple nodes automatically, in the field, without manual configuration, requires each new network node or terminal to both announce itself to the other nodes in the network, and sense the other network nodes that use the same radio frequency (RF) waveform. Network nodes are sometimes referred to as network devices, and such a process is sometime referred to as network joining.
In one network implementation, sometimes referred to as a network layer 1 and layer 2 implementation, a spatial time division multiple access (STDMA) technique is utilized for joining. This joining implementation minimizes mutual interference with other mobile terminals of the same type, enhances scalability of the network, and reduces the probability of interception. In such a network implementation, linking, or joining communication between two terminals is pre-coordinated and scheduled in specified TDMA time slots. Since a single frequency and bandwidth are used, joining communications are half-duplex. One terminal, or node, is scheduled to transmit while the other terminal, or node, is scheduled to receive for a given time slot.
Spatial separation is accomplished by these typically wireless terminals through employment of phased array antennas (PAA) that have high gain and narrow beams that specifically point at each other. These antennas operate based on line-of-sight (LOS) and point-to-point operation to close the wireless link communication within that scheduled time slot. Outside of the LOS beam link, reception is impaired due to the transmitter power being set to just achieve link closure within a set margin. Link closure for communication is only accomplished by having the same RF waveform, a pre-negotiated slot and transmit/receive assignment, a known position to the terminal in which another terminal is trying to communicate, and a known range between the two terminals. Given that a mobile terminal is trying to discover another mobile terminal without a priori knowledge of the above consideration, a methodology is needed so that these two mobile terminals (network devices) can quickly discover one another within a network.